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Classification of Elements and Periodicity in Properties

Multiple Choice Questions

141.

Among the following groupings which represent the collection of isoelectronic species.

NO⁺, C $_{2}^{2 -}$ , C $_{2}^{-}$ , CO
N₂, C $_{2}^{2 -}$ , CO, NO
CO, NO⁺, CN^-, C $_{2}^{2 -}$
NO, CN^-, N₂, O $_{2}^{-}$

142.
Which element has maximum first ionisation potential?

Cs

F

Na

He

Atoms and ions having inert gas configuration (such as helmm), i.e. stable (half-filled) configuration have high ionisation potential, i.e. it is relatively easy to remove an electron from a partially filled valence shell, where Z_eff is lower but it is relatively difficult to remove an electron from an atom or ion that has a filled valence shell, where Z_eff is higher.